CoCo VMs On Linux Will Now Panic If RdRand Is Broken To Avoid Catastrophic Conditions

For confidential computing "CoCo" virtual machines where the VM host is assumed to be un-trusted and aims to be as isolated as possible, RdRand hardware random number generator instructions are one of the limited sources of entropy for guest VMs. Right now RdRand can fail and the CoCo guest VMs will continue to boot albeit with limited or no entropy to see the VM's random number generation. But being merged today as part of x86 fixes for Linux 6.9 is now requiring seeding RNG with RdRand for CoCo environments otherwise a kernel panic...